Avian Influenza A (H5N1) : Situation Update

The Public Health Agency of Canada continues to closely monitor and report on occurrences of avian influenza H5N1, or “bird flu”, in humans and in birds.

Latest Developments

Family Cluster of Human Infection with the H5N1 Avian Influenza Virus, Indonesia -

Indonesia 's ministries of health and agriculture and WHO epidemiologists are investigating a cluster of cases involving seven members of an extended family in Kubu Sembelang village, Karo District, of North Sumatra, in Indonesia. All confirmed cases in the cluster can be directly linked to close and prolonged exposure to an infected family member during a phase of severe illness and six of the seven live in close proximity to each other.

At this time, the possibility of human-to-human transmission cannot be ruled out; however, authorities continue to investigate for a possible alternate source of infection. Furthermore, intensified investigation and surveillance have revealed no evidence of spread within the general community and no evidence that efficient human-to-human transmission has occurred.

Summary of H5N1 Avian Influenza Situation in Humans

Infection in humans has occurred in three distinct waves of activity, since late-December 2003. The current wave of activity has been ongoing since December 16, 2004. Countries reporting human cases of H5N1 are listed in Table 1.

For an up-to-date account of human cases of H5N1by region and time period, visit the following WHO page: Cumulative Number of Confirmed Human Cases of Avian Influenza A/(H5N1) Reported to WHO.

Summary of H5N1 Avian Influenza Situation in Birds

In recent months, the avian influenza H5N1 virus has been confirmed in wild birds in several countries in the following regions: Asia, Europe, and Africa. While this demonstrates the rapid and ongoing geographical spread of the virus, information to date has shown that the greatest risk to humans arises when the virus becomes established in small backyard poultry flocks, which allow continuing opportunities for close human contact , exposure, and infection to occur. To date, almost all cases have been linked to close contact with diseased household poultry flocks; there has been no evidence of direct transmission to humans from wild birds.

Information on Avian Influenza A (H5N1)

Avian influenza H5N1 is a contagious viral infection that is thought to affect all species of birds; although rare, infection in humans can occur. The first documented infection of human outbreaks with the avian influenza H5N1 virus occurred in Hong Kong in 1997, when the strain caused severe respiratory disease in 18 humans, six of whom died. The infection in humans coincided with an epidemic of H5N1 in Hong Kong's domestic poultry population. A slightly different version of this H5N1 virus arose in 2003 and is currently spreading among poultry and wild birds in parts of Asia, Europe and Africa. These outbreaks in birds have resulted in humans also acquiring this infection.

Investigation into human cases of H5N1 suggests that direct contact with infected poultry has been the primary, if not exclusive, means of infection; although, in a small number of instances a link to direct contact with infected poultry was not identifiable. In a few cases, it would appear that limited human-to-human transmission may have occurred. However, such cases involved extended close personal contact with an infected individual (i.e. providing bedside care for an infected relative) and no further transmission occurred. Overall given the broad circulation of this virus in wild and domestic birds and the number of humans that have been exposed to these sick and dead birds, human infection resulting is severe illness remains a relatively rare event.

Antiviral Drugs for Influenza

There are two classes of antiviral drugs currently available by prescription for the prevention or treatment of seasonal influenza in Canada. One class (which includes the drug amantadine) is not currently recommended for treatment of seasonal or novel (new or unusual) influenza viruses, including H5N1 avian influenza, due to concerns regarding resistance. These concerns, together with the lack of surveillance data on antiviral resistance in many parts of the world, also limit the value of prescribing this class of drugs as prophylaxis (preventative medication).

The other class of drugs, which include oseltamivir (Tamiflu®) and zanamivir (Relenza®) have the best potential to treat illness due to seasonal influenza or novel influenza viruses. This second class is known to decrease the duration of illness (by approximately 1 day) and reduce the chance of developing the most severe form of the illness. Oseltamivir has been used for the treatment of H5N1 influenza; however, its use has been sporadic and frequently not early enough in the course of the illness to determine how well it works against this novel infection. There is no data on the use of Relenza for the treatment of H5N1. Nevertheless, this class of drugs is expected to be the most effective treatment for novel influenza infections provided it is initiated within the first 48 hours of symptom onset. These drugs are generally well tolerated and unlike the other class of antivirals, drug resistance is rarely reported. The efficacy of oseltamivir and zanamivir for the prevention of H5N1 illness has not been studied but is expected to be consistent with the 70-90% efficacy demonstrated for seasonal influenza strains.

Recommendations

As a precautionary measure, the Public Health Agency of Canada recommends that it would be prudent for travellers to countries listed in Table 2 of the advisory to consider the following measures:

Avoid unnecessary contact with domestic poultry and wild birds . This includes poultry farms as well as markets where live and slaughtered animals such as chickens and ducks are sold, as these animals have been found to be carriers of the avian influenza A (H5N1) virus. Evidence suggests that the risk of infection is greatest in persons having direct contact with live and/or dead poultry including surfaces contaminated with their feces or secretions. Travellers should be aware that it is possible for the avian influenza A (H5N1) virus to stick to hair and clothing, and may be inhaled.

Ensure that all fowl (domestic poultry and/or wild birds) prepared for consumption is thoroughly cooked (juice runs clear and no visible pink meat) to eliminate the risk of infection. Internal temperatures for whole fowl and parts should reach 82°C-85°C. While to date there is no evidence that the virus is transmitted through contaminated food, it is always advisable to avoid undercooked or raw fowl dishes, including eggs and egg products.

Follow normal precautions regarding food storage, handling and preparation. Travellers are advised to maintain high standards of hygiene, including thorough hand washing, particularly after having contacted eggs or undercooked fowl and egg products and to avoid cross contamination with other food products. Using hot, soapy water and lathering for at least 20 seconds is the single most important procedure for preventing infections. This is because disease-causing micro-organisms can frequently be found on the hands. Alternatively, travellers can use waterless, alcohol-based antiseptic hand rinses. If there is visible soiling, hands should be washed with soap and water before using waterless antiseptic hand rinses. If soap and water are unavailable, cleanse hands first with detergent-containing towelettes to remove visible soil.

Get your annual flu-shot. At this time, there is no vaccine available that protects against the avian influenza A (H5N1) virus. The current seasonal flu vaccine does not protect against the avian (H5N1) virus. To avoid illness due to circulating human influenza viruses, travelers should consider immunization with the most current available seasonal flu vaccine.

Antivirals: The Public Health Agency of Canada does not routinely recommend the use of antiviral drugs as prophylaxis (preventative medication) or to carry as standby treatment for Canadians travelling to areas where H5N1 infection has been reported in birds or humans.

However, in exceptional circumstances, the advanced prescription and procurement of antivirals for prophylaxis or treatment may be considered for specific travellers who, following an individual risk assessment with their personal physician or travel clinic, may be deemed at increased risk of exposure to the virus, such as those involved in the culling of birds; providing veterinary support in the investigation or control of H5N1 in birds; assisting in an epidemiologic investigation of H5N1 cases among birds or humans; or those providing health care to human H5N1 cases.

Canadian Food Inspection Agency recommendations to prevent the introduction of avian flu into Canada's animal population:

• Ensure all birds and poultry products you wish to bring into Canada are eligible for entry and declare all animal products upon arrival.
• Travellers who have visited a farm while in an affected country should ensure that clothing and footwear worn on the farm are free from soil and manure before entering Canada. Clothing should be laundered and footwear should be disinfected after arrival. More information is available at the Canadian Food Inspection Agency.

As a reminder…

The Public Health Agency of Canada routinely recommends that Canadian international travellers seek the advice of their personal physician or travel clinic four to six weeks prior to international travel, regardless of destination, for an individual risk assessment to determine their individual health risks and their need for vaccination, preventative medication, and personal protective measures.

The Public Health Agency of Canada recommends, as well, that travellers who become sick or feel unwell on their return to Canada should seek a medical assessment with their personal physician. Travellers should inform their physician, without being asked, that they have been travelling or living outside of Canada, and where they have been.

Additional Information

Information on Avian Influenza from the Public Health Agency of Canada

• Avian Influenza information page
• FAQ on Avian Influenza
• Archived travel health advisories on avian influenza]

Information on Influenza from the Public Health Agency of Canada

Advisory Committee Statements

• Committee to Advise on Tropical Medicine and Travel (CATMAT) Statement on Travel, Influenza, and Prevention
• National Advisory Committee on Immunization (NACI) Statement on Influenza Vaccination for the 2005-2006 Season

Other related information from the Public Health Agency of Canada

• FluWatch weekly report summarizes influenza surveillance activities in Canada and abroad.
• Antivirals

External Sources of Information

For additional information on Avian Influenza A (H5N1) from the World Health Organization (WHO) visit the WHO Avian Influenza Disease Page .

For an updated account of human cases of H5N1by region and time period, visit the following: Cumulative Number of Confirmed Human Cases of Avian Influenza A/(H5N1) Reported to WHO .

For international reports of the flu, visit the World Health Organization influenza web site .

For international reports of infected animals by country, visit the World Organization for Animal Health .